Press felt

Abstract

The invention relates to a press felt for the transportation of a web and for the dewatering thereof in a press part of a paper machine. The press felt comprises at least one needled flock layer formed by fibres. In order to eliminate the re-wetting and the blow effect, a surface layer is formed on or partially within the flock layer at least on one side of the felt. The permeability of the surface layer is substantially lower than that of the rest of the felt beneath the surface layer. The surface layer can be formed by a plastic material applied on the flock layer.

I claim: 
     
       1. A press felt for the transportation of a web and the dewatering thereof in a press part of a paper machine, said press felt comprising at least one needled flock layer of fibres provided with a surface layer formed on or partially within the flock layer on at least one side of the felt, the permeability of said surface layer being substantially lower than that of the rest of the felt beneath the surface layer. 
     
     
       2. The press felt of claim 1, wherein the surface layer is formed of a plastic material applied on the flock layer. 
     
     
       3. The press felt of claim 1 wherein the permeability of the surface layer ranges from about 0 to about 2 m 3  /m 2  /min. 
     
     
       4. The press felt of claim 2, wherein the permeability of the surface layer ranges from about 0 to about 2 m 3  /m 2  /min. 
     
     
       5. The press felt of claim 1, wherein the one side of the felt where said surface layer is formed has a substantially reduced pore size when compared with the remainder of the felt.   
     
     
       6. The press felt of claim 5, wherein said surface layer has a higher permeability to water than said web and a lower permeability to water than the remainder of the felt.   
     
     
       7. The press felt of claim 2, wherein said plastic material is selected from the group consisting of acrylic resins, styrene butadiene resins, polyvinyl chlorides and polyurethanes.   
     
     
       8. The press felt of claim 1, comprising one surface layer formed on the side of the felt which contacts the web.   
     
     
       9. The press felt of claim 1, comprising first and second surface layers; said first layer formed on the side of the felt which contacts the web, and said second layer formed on the side opposite said web contacting side of the felt.   
     
     
       10. The press felt of claim 9, wherein said first and second layers have the same permeability to water.   
     
     
       11. The press felt of claim 9, wherein said second layer has a lower permeability to water than said first layer.   
     
     
       12. The press felt of claim 1, wherein said surface layer is formed on the surface of the press felt.   
     
     
       13. The press felt of claim 12, wherein said surface layer is further formed within the flock layer of the felt.